Tools

Measurement of Numerical Aperture.

Procedure

  1. Connect the circuit by using the circuit diagram.
  2. Plug the AC mains. Light should appear at the end of the fiber on the NA fig. 1 The light intensity should increase.
  3. Hold the screen, provided in the Kit vertically at a distance of 15 mm (L) from the emitting fiber end and view the red spot on the screen. A dark room will facilitate good contrast. Position the screen-cum-scale to measure the diameter (W) of the spot. Choose the largest diameter.
  4. Compute NA from the formula
     NA = sinθmax=W/(4L2+W2)½
    Repeat the experiment for 10mm and 25mm distance of the screen.
  5. Calculate the acceptance angle θa = sin-1(NA).

Figure 1: Set up for Measurement of NA